Corrosion inhibitor



Patented .lan. 1% i943 CORROSION WHIBITOR Louis H. Howland, Cheshire, Conn, and William P. tot Horst, Packanack Lake, N. J., assignors to United States Rubber Company, New York, N. Y., a corporation of New Jersey No Drawing. Original application December 28,

1937, Serial N0.

now Patent No.

2,196,261, dated April 9, 1940. Divided and this application September 30, 1939, Serial No.

2 Claims.

This invention relates to corrosion inhibitors or retarders for protecting metal surfaces, and particularly those of ferrous and related metal or alloy products, from the corrosive or oxldative action of air or oxygen in the presence of moisture or aqueous or other liquids.

This application is a division of our application Serial No. 182,170, filed Dec. 28, 1937, now U. S. Patent No. 2,196,261, issued April 9, 1940.

Iron and steel products after the pickling operations are usually coated with so-called slushing oils to prevent rusting, but such oils per se have not been found sufllciently eiiective to prevent the corrosion. The present invention aims to provide chemicals which may be employed with such oils to reduce the corrosion of the metal. It further aims to provide chemicals as corrosion inhibitors for metal surfaces wherever the metal comes in contact with fluids causing or tending to cause corrosion of the metal surface, for example, the chemical may be incorporated in liquids used in cooling systems of internal combustion engines such as monohydric or polyhydric alcohols, in lubricating oils, in textile oils, in shock absorbers, in hydraulic lifts, etc.

The corrosion inhibitors of the present invention are compounds of the general formula wherein X and X1 are hydrogen, alkyl, or aralkyl, that is, are nitrogenous compounds containing one or more aralkyl substituents directly linked to an amino nitrogen atom. These compounds are also broadly, ammonia compounds in which at least one, and preferably not more than two of the hydrogens connected to the nitrogen atom, has been replaced by an aralkyl group, the allphatic portion of the radical being directly connected to the nitrogen atom. Compounds which are particularly effective are the benzylamines. such as monobenzylamine, dibenzylamine, and mixtures thereof. One way of preparing such compounds is by reacting an aralkyl halide, e. g. benzyl chloride, with excess aqueous ammonia, under pressure in an autoclave, e. g. at about 130 0., and isolating, or not, the desired reaction products from the crude reaction product by distillation.

In one such method 605 pounds of aqua ammonia heated to about 120 C. at a pressure of about 250 lbs. per square inch, has slowly added to it about 250 pounds of benzyl chloride. The reaction temperature is about 130 C. and is maintained about 1 hour, at the end of which time the pressure usually has dropped to approximately 170 lbs. per square inch, after which the mix is cooled and treated with about 300 pounds or a caustic soda solution to liberate excess ammonia which may be recovered for re-use in the process. The oily layer which separates out is a crude mixture of benzylamines and may be fractionally distilled in vacuo thereby recovering a fraction boiling at -100 C. at 5-10 mm. Hg which consists largely of monobenzylamine, as well as a fraction boiling at -200 C. at 5-10 mm. Hg which is chiefly dibenzylamine. These two products may be blended, a desirable blend being one containing about 75% dibenzylamlne and about 25% monobenzylamine. However, the crude reaction mixture may be used as such for corrosion inhibiting purposes.

The following examples employing a product composed essentially of dibenzylamine and monobenzylamine illustrate the effectiveness of this class of corrosion inhibitors:

Example 1.--Fresh1y pickled steel plates were weighed and added to a 15%, by volume, alcohol-water solution. The alcohol solution contained .12% soap and .12% of a product consisting essentially of 25% monobenzylamine and 75% dibenzylamine. The solution was heated to 60 C. and air was bubbled through rapidly for 26 hours. The amount of corrosion was determined by visual observation and by increase in weight. The results were as follows:

Blank (soap Soap solution-{- solution) 1 inhibitor Weight increase .061 gram .007 gram. Visual test Heavy rust No rust.

Example 2.Pieces of steel, hot rolled tin plate stock, 3"x4", which had been pickled, were coated with so-called slushing oils. Another set of steel pieces were pickled and coated with slushing oil containing 1% of the same inhibitor. It was observed that the steel pieces coated with slushing oil gradually rusted; whereas, the steel plates coated with slushing oil containing the inhibitor remained bright and free from rust.

In some cases where the alkalinity of the inhlbitors may render certain media unduly corrosive towards metals or alloys, it is advisable to neutralize the inhibitor as by the addition of phosphoric acid, oleic acid, palmitic acid or isttearic acid thereby providing a salt of the inhib- Examples of other aralkylamines within the scope of the invention are aliryl benzylamines such as methyl benzyiamine, ethyl benzylamine, isopropyl benzylamine, beta-phenylethylamine, etc.

The addition of soap greatly increases the eflectiveness of the inhibitors, especially when used in aqueous media.

The addition of the inhibitors to oils that are commonly used to keep tools and machinery from rusting or to keep pickled steel from rusting on storage or in transit greatly increases the antirust properties of such oils. Other uses are for petroleum oils (refined and/or in crude oils that contain sulphur), air-conditioning systems (humidiflcation), tire molds, valves, bead-wire for tires, boilers (boiler water) fire extinguisher solutions, etc.

The inhibitors should be used in quantity sufflcient to inhibit the corrosion of the metal, .1 to 5% by weight of the inhibitor being ordinarily sumcient.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. An anti-rusting oil for inhibiting the corrosion oi metals which comprises a mineral oil and a minor proportion of a dibenzylamine compound selected from the class consisting of dibenzylamine and higher fatty acid salts thereof to inhibit the corrosion of the metal.

2. An anti-rusting oil for ferrous metals which comprises a mineral oil and a minor proportion of dibenzylamine to inhibit the corrosion of the metal.

LOUIS H. HOWLAND. WILLIAM P. ran HORST. 

